Fig. 1. Stable phases on the convex hulls of Ca-N system at 100 GPa.

Fig. 2. Crystalline structure of the predicted stable Ca₅N₄: (a) P 2₁/c phase at 100 GPa; (b), (c) he polyhedron units of Ca₅N₄.

Fig. 3. Phonon dispersion curves of P 2₁/c phase at 100 GPa

Fig. 4. Cross-sections of electron local function of P 2₁/c-Ca₅N₄ at 100 GPa.

Fig. 5. Band structure and projected density of states of P 2₁/c-Ca₅N₄ at 100 GPa, respectively.

Fig. 6. Raman spectrum of P 2₁/c-Ca₅N₄ at 100 GPa.

Fig. 7. The X-ray diffraction spectrum of P 2₁/c-Ca₅N₄ at 100 GPa.